Hot-dip aluminum alloy plated steel having excellent shear cut edge corrosion resistance and processed part corrosion resistance, and method of manufacturing the same

Abstract

The hot-dip aluminum alloy plated steel has a base steel and a plated layer, in which the composition of the plated layer contains, by % by mass, Fe: 25% to 75%, Mg: 2% to 20%, and Ca: 0.02% to 2% with a remainder of Al and inevitable impurities, the plated layer contains one or both of an α-Mg phase and an Al 3 Mg 2 phase, and the sum of the partial volume fraction of the α-Mg phase and the partial volume fraction of the Al 3 Mg 2 phase in a range of a depth of 5 μm from a surface of the plated layer is 1% to 40%.

The invention claimed is: 
     
       1. A hot-dip aluminum alloy plated steel comprising a base steel and a plated layer, wherein:
 a composition of the plated layer contains, by % by mass, Fe: 25% to 75%, Mg: 2% to 20%, and Ca: 0.02% to 2% with a remainder of Al and inevitable impurities; 
 the plated layer contains one or both of an α-Mg phase and an Al 3 Mg 2  phase; and 
 a sum of a volume fraction of the α-Mg phase and a volume fraction of the Al 3 Mg 2  phase in an area that is from a surface of the plated layer to a depth of 5 μm is 1% to 40%. 
 
     
     
       2. The hot-dip aluminum alloy plated steel according to  claim 1 , wherein the volume fraction of the α-Mg phase is 0.4% to 20%. 
     
     
       3. The hot-dip aluminum alloy plated steel according to  claim 1 , wherein the volume fraction of the Al 3 Mg 2  phase is 0.1% to 40%. 
     
     
       4. The hot-dip aluminum alloy plated steel according to  claim 2 , wherein an amount of Fe contained in the composition of the plated layer is 40% to 55%. 
     
     
       5. The hot-dip aluminum alloy plated steel according to  claim 3 , wherein an amount of Fe contained in the composition of the plated layer is 30% to 50%. 
     
     
       6. The hot-dip aluminum alloy plated steel according to  claim 1 , wherein the composition of the plated layer further contains, by % by mass, at least one of Si: 0.0001% to 2%, REM: 0.0001% to 1%, or Sr: 0.0001% to 2%. 
     
     
       7. The hot-dip aluminum alloy plated steel according to  claim 6 , wherein the REM is an La—Ce alloy. 
     
     
       8. A hot-dip aluminum alloy plated steel, wherein coating is applied on the hot-dip aluminum alloy plated steel according to  claim 1 . 
     
     
       9. A method of manufacturing the hot-dip aluminum alloy plated steel according to  claim 1 , the method comprising:
 a plating process in which the base steel is immersed in a plating bath; and 
 an alloying thermal treatment process in which the base steel is held at a temperature of 500° C. or higher, and 700° C. or lower, for a duration of more than 3 seconds and 60 seconds or less in a state in which the base steel is immersed in the plating bath or after the base steel is removed from the plating bath. 
 
     
     
       10. A method of manufacturing the hot-dip aluminum alloy plated steel according to  claim 2 , the method comprising:
 a plating process in which the base steel is immersed in a plating bath; and 
 an alloying thermal treatment process in which the plated base steel is heated at a temperature of 500° C. or higher, and 700° C. or lower, for a duration of more than 3 seconds and 60 seconds or less after the base steel is removed from the plating bath. 
 
     
     
       11. A method of manufacturing the hot-dip aluminum alloy plated steel according to  claim 3 , the method comprising:
 a plating process in which the base steel is immersed in a plating bath; and 
 an alloying thermal treatment process in which the base steel is held at a temperature of 500° C. or higher, and 700° C. or lower, for a duration of more than 3 seconds and 60 seconds or less in a state in which the base steel is immersed in the plating bath, 
 wherein no alloying thermal treatment is performed after the plated base steel is removed from the plating bath.